1. Technical Field
The present invention relates to rollers disposed on transporting paths of recording media in recording apparatuses typified by facsimiles, printers, and the like, and relates to recording apparatuses and liquid ejecting apparatuses including the rollers. Moreover, the invention relates to apparatuses for molding the rollers, molds for forming the rollers, and methods for producing the rollers.
2. Related Art
Herein, an ink jet printer will be described as an example of a recording apparatus. An ink jet printer usually includes a transporting unit for transporting recording sheets, serving as an example of recording media, upstream of an ink jet recording head. The transporting unit includes a driving roller and driven rollers pressed into contact with the driving roller so as to be rotated in response to the rotation of the driving roller. When the driving roller is rotated while a recording sheet is pinched between the driving roller and the driven rollers, the recording sheets are transported to an area opposing the ink jet recording head. JP-A-11-286348, JP-A-11-314789, and JP-A-2001-97593, for example, disclose driven rollers pressed into contact with a driving roller so as to be rotated in response to the rotation of the driving roller.
Since the driven rollers are firmly pressed into contact with the recording surface of the recording sheet, roller traces can remain on the recording surface when burrs or the like exist on the outer circumferential surfaces of the rollers. In particular, ends (edges) of the driven rollers in an axial direction can be easily sharpened, and burrs can also be easily created on the outer circumferential surface of the driven rollers. Therefore, the external diameter of the driven roller described in JP-A-2001-97593 at the central portion thereof in the axial direction is increased as compared with those at either end thereof such that both ends of the driven roller in the axial direction, which can be easily sharpened, are prevented from coming into contact with recording sheets.
As shown in FIG. 3 in JP-A-2001-97593, a mold for forming driven rollers has mold gates at first end surfaces of the rollers in a direction along a rotating shaft (hereinafter simply referred to as “first end surfaces of the rollers”). The mold gates are located at the first end surfaces of the rollers since gate bosses (protrusions) remain on the outer circumferential surfaces of the rollers and can damage the recording surfaces of the recording sheets if the mold gates are located at the outer circumferential surfaces of the rollers.
However, when the mold gates are located at the first end surfaces of the rollers, the gate bosses are formed on the first end surfaces, and increase sliding loads between the driven rollers and regulating members for regulating the positions of the driven rollers in the direction along the rotating shaft. This disadvantageously prevents smooth rotation of the rollers. Moreover, in order to solve this problem, a secondary process such as grinding is sometimes required to remove the gate bosses.
In addition, the ends of the outer circumferential surfaces of the rollers can protrude outward (in radial directions) even when the mold gates are located at the first end surfaces of the rollers since a high pressure is applied to resin adjacent to the mold gates. As a result, the ends of the outer circumferential surfaces of the rollers can be firmly pressed into contact with the recording surfaces of the recording sheets, and can damage the recording surfaces.